Remove SetStateUnsafe in Debugger::Disconnected.

The debugger thread has the exclusive mutator lock and doen't need to
switch to runnable while updating instrumentation.

This avoids a spurious failure of the DCHECK in the jdwp test.

Bug: 25262836

Change-Id: Ibfd0bc3936a877fd264396fcc4cc1af8d19a1645
2 files changed